Dornback 45K garage ceiling heater will not continue to run !!

A one month old Dornback 45K NG garage ceiling mount heater will not continue to run. The surface temp ignitor and control box has been sent back to the factory and bench tested OK. The unit ignites burners but after 3-5 seconds the burners go out and cyle starts over. This happens for 3 cycles then unit shuts down. Factory tech is sending another ignitor to try!! Any ideas or assistance would be greattly appreciated. Thanks